Health care providers are at risk of being infected by a needle prick from a blood contaminated needle each time they withdraw a hypodermic type needle from a patient. This is particularly true when the hypodermic type needle is not secured to the end of an elongated, rigid syringe but to a patient attachable structure such as a butterfly needle holding assembly. It would be desirable, therefore, to have a needle cover assembly for covering the hypodermic type needle attached to a butterfly needle holding assembly as soon as the tip of the hypodermic type needle is withdrawn form the patient. To ensure the cover remains over the tip of the hypodermic type needle, it would be a further benefit to have a needle retaining mechanism that allowed the needle to easily enter a needle receiving cavity of the cover but which provided resistance to the needle moving out of the cover where it could prick and possibly contaminate a health care worker.